CRM-6773 Print PDF Contribution Receipts is broken was event related contribution

Steps to replicate:
1. Find Contribution
2. Select event related contributions, and use "Print or Email Contribution Receipt" and hit Go.
3. Print PDF

PDF is generated with "nothing"

We should check contribution related to following scenarios:
1. DIsable confirmation email option for event and then print contribution receipt for that event.
2. Print receipt for the contact without any email address.